Controlling the supply of bodyfeed to a filter

Abstract

The invention features a control system for controlling the supply of bodyfeed to a filter for removing solids from a beer stream is described. By applying the bodyfeed at an appropriate rate and hence achieving appropriate effective bed voidage it is possible to maintain beer clarity while minimizing filter aid usage. The control system includes a means for determining turbidity of the liquid stream upstream of the filter, a means for determining the rate of pressure drop change across the filter, and a controller for altering the supply of bodyfeed to the filter in accordance with a calculated dose change.

The claims defining the invention are as follows:  
     
       1. A control system for controlling the supply of bodyfeed to a filter for removing solids from a liquid stream, including: 
       turbidity determining means for determining turbidity of the liquid stream upstream of the filter;  
       pressure drop change determining means for determining the rate of pressure drop change across the filter and trend of pressure drop change rate; and  
       a controller having dose change calculation means for calculating one of an unchanged dose, a small dose change, and a dose change from a determined turbidity and a determined rate of pressure drop change, and trend of pressure drop change rate and altering means for altering the supply of bodyfeed to the filter in accordance with a calculated dose change.  
     
     
       2. A control system as claimed in  claim 1 , wherein the dose calculation means is a fuzzy controller. 
     
     
       3. A control system as claimed in  claim 2 , wherein the fuzzy controller calculates the dose change in accordance with the following set of rules: 
       IF rate of pressure drop change is low AND trend of rate of pressure drop change is increasing AND turbidity is low THEN dose change is zero  
       IF rate of pressure drop change is low AND trend of rate of pressure drop change is steady AND turbidity is low THEN dose change is −small  
       IF rate of pressure drop change is low AND trend of rate of pressure drop change is decreasing AND turbidity is low THEN dose change is −large  
       IF rate of pressure drop change is ideal AND trend of rate of pressure drop change is increasing AND turbidity is low THEN dose change is +small  
       IF rate of pressure drop change is ideal AND trend of rate of pressure drop change is steady AND turbidity is low THEN dose change is zero  
       IF rate of pressure drop change is ideal AND trend of rate of pressure drop change is decreasing AND turbidity is low THEN dose change is −small  
       IF rate of pressure drop change is high AND trend of rate of pressure drop change is increasing AND turbidity is low THEN dose change is +large  
       IF rate of pressure drop change is high AND trend of rate of pressure drop change is steady AND turbidity is low THEN dose change is +small  
       IF rate of pressure drop change is high AND trend of rate of pressure drop change is decreasing AND turbidity is low THEN dose change is zero  
       IF turbidity is high THEN dose change is +very large.  
     
     
       4. A control system as claimed in  claim 3 , wherein the dose change calculation means includes aggregating means for aggregating the rules when more than one rule is fired so that said dose change is based on the aggregation of said rules. 
     
     
       5. A control system as claimed in  claim 4 , wherein said aggregating means aggregates said rules in accordance with weightings allocated to each of said rules. 
     
     
       6. A control system as claimed in  claim 5 , wherein the rule where turbidity is high is given a greater weighting than the rules where turbidity is low. 
     
     
       7. A control system as claimed in  claim 6 , wherein the rule where turbidity is high is given a weighting approximately ten times the weighting of the rules where turbidity is low. 
     
     
       8. A control system as claimed in any of  claim 1  or any of claims  2 - 7 , wherein the liquid stream is a beer stream. 
     
     
       9. A method for controlling supply of bodyfeed to a filter for removing solids from a liquid stream, including: 
       determining turbidity of the liquid stream upstream of the filter;  
       determining the rate of pressure drop change across the filter and trend of pressure drop change rate; and  
       calculating one of an unchanged dose, a small dose change, and a large dose change from the determined turbidity and the determined rate of pressure drop change, and trend of pressure drop change rate and altering the supply of body feed to the filter in accordance with the calculated dose change.  
     
     
       10. A method as claimed in  claim 9 , wherein dose change is calculated by a fuzzy controller. 
     
     
       11. A method as claimed in  claim 10 , wherein the fuzzy controller calculates the dose change in accordance with the following set of rules: 
       IF rate of pressure drop change is low AND trend of rate of pressure drop change is increasing AND turbidity is low THEN dose change is zero  
       IF rate of pressure drop change is low AND trend of rate of pressure drop change is steady AND turbidity is low THEN dose change is −small  
       IF rate of pressure drop change is low AND trend of rate of pressure drop change is decreasing AND turbidity is low THEN dose change is −large  
       IF rate of pressure drop change is ideal AND trend of rate of pressure drop change is increasing AND turbidity is low THEN dose change is +small  
       IF rate of pressure drop change is ideal AND trend of rate of pressure drop change is steady AND turbidity is low THEN dose change is zero  
       IF rate of pressure drop change is ideal AND trend of rate of pressure drop change is decreasing AND turbidity is low THEN dose change is −small  
       IF rate of pressure drop change is high AND trend of rate of pressure drop change is increasing AND turbidity is low THEN dose change is +large  
       IF rate of pressure drop change is high AND trend of rate of pressure drop change is steady AND turbidity is low THEN dose change is +small  
       IF rate of pressure drop change is high AND trend of rate of pressure drop change is decreasing AND turbidity is low THEN dose change is zero  
       IF turbidity is high THEN dose change is +very large.  
     
     
       12. A method as claimed in  claim 1 , wherein dose change is calculated by aggregating the rules when more than one rule is fired so that said dose change is based on the aggregation of said rules. 
     
     
       13. A method as claimed in  claim 12 , wherein said rules are aggregated in accordance with weightings allocated to each of said rules. 
     
     
       14. A method as claimed in  claim 13 , wherein the rule where turbidity is high is given a greater weighting than the rules where turbidity is low. 
     
     
       15. A method as claimed in  claim 14 , wherein the rule where turbidity is high is given a weighting approximately ten times the weighting of the rules where turbidity is low. 
     
     
       16. A method as  claim 9  in any of claims  10 - 15 , wherein the liquid stream is a beer stream.